1. Intro (I) Flashcards Preview

Elsevier Bacteriology (RVSP) > 1. Intro (I) > Flashcards

Flashcards in 1. Intro (I) Deck (55)
Loading flashcards...
1

Bacteria that are not stained through Gram Staining

Chlamydia
Legionella
Mycoplasma

2

Gram stain procedure

Crystal violet (1° stain)
Gram's iodine (Mordant)
Acetone / alcohol (Decolorizer)
Safranin (Counterstain)

COAM

3

What is the difference between Gram+ and Gram- cell walls?

Cell walls of gram-negative cells have higher lipid content that gram-positive cells

4

Special consideration of Gram Stain of sputum specimen; if >25 epithelial cells/lpf

Saliva

5

Special consideration of Gram Stain of sputum specimen; few epithelial cells, many PMN cells

Specimen more likely to yield a pathogen

6

When can you say that a sputum specimen is actually saliva?

When there are >25 epithelial cells/lpf

7

When can you say that a sputum specimen may likely yield a pathogen?

When there are few epithelial cells and many PMN cells

8

Special consideration for urine specimen

1 cell per oil immersion field = approx. 1x10^5 CFU/mL

9

Enumerate the quantitation criteria for Gram Stain

- no organisms seen
- Few per slide = rare
- 0 to 2 per field = few
- 2 to 10 per field = moderate
- more than 10 per field = many

10

Constituents of media

Agar
Nutrients
Enrichments
Buffers
pH indicators
Inhibitors

BEANpI

11

Constituent of media; gelatinous seaweed extract

Agar

12

Percent of agar in plates

1-2% agar in plates

13

Nutrients in media can be _______ or _______

Hydrolyzed proteins (animal or plant)
Carbohydrates/sugars

14

Enrichments used in media

Yeast extracts
Blood

15

Purpose of buffers in media

Provides a stable pH for growth

16

pH indicators used in media and their colors

Neutral red: red to colorless
Phenol red: yellow to red
Thymol blue: yellow to green/blue

17

Inhibitors in media

Bile salts
Antibiotics
Dyes
Sodium chloride
Sodium citrate

BADSS

18

Examples of dyes used as inhibitors in media

Crystal violet
Eosin
Methylene blue

19

Example of bile salt used as inhibitor in media

Sodium deoxycholate

20

Agar that contains inhibitory agents to all organisms except one being sought

Selective agar

21

Example of selective agars

Colistine nalidixic acid agar (CNA)
MacConkey Agar

22

Agar that selects for certain organisms to the disadvantage of others

Selective agar

23

Agar that allows organism to be morphologically distinguished from other organisms with different characteristics

Differential agar

24

Examples of differential agar

Sheep blood agar (SBA)
MacConkey agar

25

Supportive media aerobic cultures

Blood agar
Chocolate agar

26

Selective/differential media for gram-negative aerobic bacilli

MacConkey agar
Xylose Lysine Desoxycholate (XLD) agar
Hektoen Enteric Agar (HEA)

27

Selective/differential media for gram-positive aerobic organisms

Colistin Nalidixic Acid (CNA) agar
Phenylethyl Alcohol Agar (PEA)

28

Purpose of Blood Agar for aerobes

General growth of gram-positive and gram-negative aerobes

29

Why is the Blood Agar also considered as differential aside from being supportive?

Because organisms may demonstrate hemolytic patterns

30

Chocolate agar is used for

Isolation of fastidious organisms:
- Haemophilus spp.
- Neisseria spp.
- Brucella spp.
- Capnocytophaga spp.